Several effective chemotherapeutic agents for treatment of various cancer types are very insoluble in water, requiring formulations that induce unwanted side effects. Recently, nanotherapeutic formulations such as Abraxane® (paclitaxel-loaded albumin nanoparticles), Doxil® (doxorubicin-loaded liposomes), and others have been shown to improve the clinical toxicity profiles of the drugs, but their anti-tumor effects are only marginally better than the original drug formulations. This has been attributed in part to the relatively large size of the nanotherapeutic formulations (generally >100 nm), which limits the extent to which the drugs can penetrate into tumor mass. In some cases, this large size also causes nanotherapeutics to be trapped in the liver and reticuloendothelial system (RES). Accordingly, there is a need to develop smaller (20-80 nm) stealth and biocompatible nanocarriers for effective delivery anti-cancer drugs in vivo.
We have recently developed several novel nanocarriers for paclitaxel (PTX) or other hydrophobic drugs. These novel nanocarriers, comprising poly(ethylene glycol) (PEG) and oligo-cholic acids, can self-assemble under aqueous conditions to form core-shell (cholane-PEG) structures that can carry PTX in the hydrophobic interior. These amphiphilic drug-loaded nanoparticles are therapeutic by themselves with improved clinical toxicity profiles. More importantly, when decorated with cancer cell surface targeting ligands and/or tumor blood vessel ligands, these nanocarriers will be able to deliver toxic therapeutic agents to the tumor sites. The final size of the nanocarriers (10 to 100 nm) is tunable by using various, or a combination of, different cholane-PEG preparations. The nanocarrier components, PEG and cholic acid, are all biocompatible and largely non-toxic. Indeed, the PTX nanotherapeutics exhibited safe profile in in vivo administration for anticancer treatment in mouse models and companion dogs. However, the nanocarriers have demonstrated some hemolytic activity both in vitro and in vivo, as well as reduced loading capacity for certain drugs. Therefore, there is a need to develop nanocarriers with improved biocompatibility and versatility.
The present invention is based on the surprising discovery that certain changes to the hydrophilic and hydrophobic segments of the constituent building blocks improve the therapeutic properties without disrupting nanocarrier assembly, addressing the needs described above.